The Great Cataclysm refers to the destruction inflicted upon Britannia by the Guardian prior to Ultima IX. It is one of the most devastating events in the history of Britannia and destroyed much of the world's landmass as a result, as seen on the right (red areas indicate regions affected, often lost altogether). Many settlements were also either destroyed or vastly decimated, rendering the land a shadow of its former self.
A catalog of the destruction is as follows:
- The entire eastern section of the mainland—beginning with the stretch from Lost Hope Bay through Lock Lake—was lost, destroying the Bloody Plains and the Drylands, including the town of Vesper. Such was the upheaval, the cities of Minoc and Cove ended up where Dagger Isle had once rested. Rioting later destroyed most of Cove.
- Paws was enveloped by the Fens of the Dead, leaving the swamp-ridden remains practically uninhabitable.
- Spiritwood was destroyed as the south was sundered from the mainland. The city of Trinsic was flooded and rebuilt amidst canals.
- A huge volcanic eruption caused great upheaval in the Valorian Isles and destroyed the city of Jhelom, which was resettled as Valoria.
- The isles of the Cape of Heroes all sunk into the sea.
- The whole southern half of the Isle of the Avatar was destroyed.
- The island of Spektran and much of the eastern and western shores of Terfin were swallowed by ocean. The Gargoyles abandoned Terfin and established an underwater city, Ambrosia.
- Buccaneer's Den and New Magincia were split in two, severely damaging the cities. New Magincia was left to ruin, but Buccaneer's Den prospered.
- The Isle of Deeds was overcome by the waves of the Great Sea, causing Serpent's Hold to fall in ruins beneath the ocean. Empath Abbey was destroyed with upheavals in the west, and the Lycaeum was abandoned and nearly forgotten.
The Ultima IX Map of Britannia shows more details about the state of Britannia after the Cataclysm.
As the Cataclysm subsided, Britannia was left heavily shaken and reconstruction efforts were unable to return the land to its former glory after such colossal decimation. The remaining cities became humble approximations of their former prestige and the loss of such significant portions of the mainland ensured a long and difficult road to recovery for Britannia.
- Main article: Bob White Plot
World maps from previous drafts of Ultima IX (seen below) indicate that, while the impact upon Britannia was not insignificant, the geographical havoc unleashed by the Great Cataclysm was to have been far less extensive than in the final release. Initially, the only major changes were the channel formed by the connection of Lost Hope Bay and Lock Lake, the submergence of the Isle of the Avatar's southern half, and a river isolating the Drylands (which would disappear entirely in a subsequent revision).